The quality of a digital image is limited by imperfections of the image sensor, imperfections of the imaging objective, or both. Generally, an image formed by an imaging objective on an image sensor is subject to deviations from ideal image formation. For example, the imaging objective may form an image that has noticeable blur or distortion. The image sensor imposes electronic noise on the image. In addition, the image sensor has optical limitations that may compromise actual detection of the image formed thereon by the imaging objective. For example, each pixel of the image sensor has a limited acceptance angle, that is, each pixel is able to detect light only within a certain range of incidence angles on the image sensor. For this reason, peripherally located pixels may collect light from the imaging objective with less efficiency than centrally located pixels, resulting in vignetting of the image.
High-performance digital cameras typically use complex lens systems designed to self-compensate, to some extent, for optical aberrations. In some cases, lens systems are designed to deliver the light to the image sensor at incidence angles that are relatively uniform across the pixel array, in order to reduce image artifacts caused by the finite acceptance angle of each pixel. High-performance lens systems require high-precision manufacturing and/or additional lens elements and are therefore relatively costly to produce. However, even high-end expensive lens systems may still fail to eliminate all noticeable image artifacts or, alternatively, have limited performance range such as a limited field of view.